The present invention relates to a scroll compressor capable of supplying a coolant gas in the least amount required to cool the motor unit.
FIGS. 5a-5d are drawings showing the operating principle of such scroll compressor. In FIGS. 5a-5d, reference numeral 1 designates a fixed scroll. Reference numeral 2 designates an orbiting scroll. Reference numeral 3 designates an suction chamber. Reference numeral 4 designates a discharge port. Reference numeral 5 designates a compression chamber. A symbol O designates the center of the fixed scroll 1.
The fixed scroll 1 and the orbiting scroll 2 have a wrap plate 1a and a wrap plate 2a, respectively, which have the same shape but whose winding direction is opposite. The wrap plates 1a and 2a are shaped to depict an involute curve, a combination of arcs or the like as is known.
Now, the operation of the fixed scroll and the orbiting scroll will be explained. The fixed scroll 1 stands still in space. The orbiting scroll 2 is combined with the stationary scroll 1 so as to be 180.degree. out of phase with the later. The orbiting scroll revolves about the center O without rotation as shown in FIG. 5(a), FIG. 5(b), FIG. 5(c) and FIG. 5(d) corresponding to 0.degree., 90.degree., 180.degree. and 270.degree. of the revolution angles of the orbiting scroll, respectively.
At the revolution angle of 0.degree. in FIG. 5(a), sealing the gas in the suction chamber 3 is completed, and the compression chamber 5 is formed between the wrap plates 1a and 2a. As the orbiting scroll 2 revolves, the volume of the compression chamber 5 gradually decreases to compress the gas in it. The compressed gas is eventually exhausted from the discharge port 4 which is formed at the center of the fixed scroll 1.
This is the structure outline of the device known as a scroll compressor.
Now, a specific structure and specific operation of the scroll compressor will be described in detail. FIG. 6 is an axial sectional view showing a conventional scroll compressor disclosed in Japanese Unexamined Patent Publication No. 117380/1983, wherein the scroll compressor is applied to a hermetic refrigerant compressor.
In FIG. 6, the fixed scroll 1 has the wrap plate 1a on one side of a base plate 1b. The orbiting scroll 2 has the wrap plate 2a on one side of a base plate 2b. The compressor includes the suction port (suction chamber) 3, the discharge port 4, the compression chamber 5 which is formed between both wrap plates 1a and 2a when the wrap plates 1a and 2a are combined with each other, a main shaft 6, an oil cap 7, a first bearing frame 8, and a second a bearing frame 9. The oil cap 7 has an suction port 7a, and is mounted so as to cover a lower portion of the main shaft 6, having a predetermined gap with the lower end of the main shaft 6. The first bearing frame 8 is provided with a depression 8a.
Reference numeral 10 designates a motor rotor. Reference numeral 11 designates a motor stator. Reference numeral 12 designates a shell. Reference numeral 13 designates an Oldham coupling. Reference numeral 13a designates a key which is fitted in a groove 2c formed in the orbiting scroll 2. Reference numeral 15 designates an oil reservoir which is arranged at the bottom in the shell 12. Reference numeral 16 designates a suction pipe. Reference numeral 17 designates a discharge pipe. Reference numeral 18 designates an orbiting scroll bearing which is eccentric with respect to the main shaft 6 and fixed in an eccentric hole 60a formed in an enlarged diameter portion 6a at the upper end of the shaft 6, and in which an orbiting scroll shaft 2c provided on the other side of the base plate 2b is rotatively engaged.
Reference numeral 19 designates a first main bearing for supporting the peripheral surface 61a of the enlarged diameter portion 6a at the upper end of the shaft 6. Reference numeral 20 designates a second main bearing for supporting a reduced diameter portion 6b at a lower portion of the main shaft 6. Reference numeral 21 designates a first thrust bearing for supporting the undersurface 20b of the base plate 2b with the orbiting scroll 2 in the axial direction. Reference numeral 22 designates a second thrust bearing for supporting a shoulder 6c between the enlarged diameter portion 6a and the reduced diameter portion 6b of the shaft 6 in the axial direction. Reference numeral 23 designates an oil feeding passage which is formed in the shaft 6 so as to be eccentric with respect to its axis, has an opening 23a in the lower end of the shaft 6, and communicates with the orbiting scroll bearing 18 and the second main bearing 20.
The orbiting scroll 2 has the orbiting scroll shaft 2c engaged in the main shaft 6 through the orbiting scroll bearing 18, engaging with the fixed scroll 1. The orbiting scroll 2 is supported by the orbiting scroll bearing 18 and the first thrust bearing 21 which is arranged on the first bearing frame 8.
The main shaft 6 is supported by the first main bearing 19 arranged in the first bearing frame 8, and the second main bearing and the second thrust bearing 22 which are arranged in the second bearing frame 9, both bearing frames being connected to each other in the form of socket, spigot joint or the like.
The Oldham coupling 13 is arranged between the orbiting scroll 2 and the depression 8a of the first bearing frame 8 to prevent the orbiting scroll 2 from rotating, allowing the orbiting scroll to carry out only the revolution movement.
Under such structure, the fixed scroll 1 is fastened to the bearing frames 8 and 9 by means of bolts or the like.
The motor rotor 10 and the motor stator 11 are fixed to the main shaft 6 and the bearing frame 9, respectively, by means of press fit, shrink fit, screwing or the like.
The oil cap 7 is fixed to the main shaft 6 by e.g. press fit or shrink fit.
The mechanical unit thus fabricated is housed in and fixed to the shell 12 by e.g. press fit or shrink fit with the fixed and orbiting scrolls 1 and 2 being located in an upper portion and with the motor rotor 10 and the motor stator 11 being located in a lower portion.
Now, the operation of the scroll compressor thus prepared will be explained. When the motor rotor 10 rotates, the orbiting scroll 2 starts its revolution through the main shaft 6 and the Oldham coupling 13 to commence the compression according to the operating principle as having explained with respect to FIG. 5a-5d.
At this time, a refrigerant gas is inspired in the shell 12 through the suction pipe 16, and passes through a communication hole 27 between the second bearing frame 9 and the motor stator 11, and through an air-gap between the motor rotor 10 and the motor stator 11, cooling the motor. After that, the gas passes through a communication hole 28 between the shell 12 and the bearing frames 8 and 9, and is taken through the suction port 3 formed the fixed scroll 1, into the compression chamber 5 where it is compressed. The route of the gas is indicated in arrows of solid line in FIG. 6.
The gas which has been compressed is discharged from the compressor through the discharge port 4 and the discharge pipe 17.
A lubricating oil is pumped up from the suction port 7a to and through the oil feeding passage 23 under the centrifugal pumping action offered by the oil cap 7 formed on and the oil feeding passage 23 formed in the main shaft 6. The oil lubricates the bearings 18-20, and arrives at the thrust bearing 21. Then the oil is returned to the oil reservoir 15 through oil returning holes 25 and 26 formed in the bearing frames 8 and 9. The route of the oil is indicated in arrows of dotted line in FIG. 6.
Since the conventional scroll compressor is constructed as described above, the air-gap of the motor is extremely narrow, lessening the amount of the gas passing through the motor unit. As a result, there is a problem in that sufficient motor cooling effect cannot be obtained. With regard to the communication hole through which the gas is passing in its total amount, there is a problem wherein when an inverter is used to give an increase in speed, the oil which has been splashed from the oil returning hole could be picked up between the peripheral surface of the stator and the inner wall of the shell, or the oil which has been deposited on the inner wall of the shell and the peripheral surface of the stator could flow back due to an increased flow rate of the gas, promoting the oil carry-over.
Regarding the latter problem, it is one solution that the distance between the peripheral surface of the stator and the inner wall of the shell is enlarged. Such solution has a disadvantage in that the outer diameter of the shell must be increased, rendering it impossible to make the compressor compact.